This invention relates generally to the treatment of gaseous mixtures such as sour gas to remove or reduce the levels of hydrogen sulfide therein. In the drilling, production, transport, storage, and processing of crude oil, including waste water associated with crude oil production, and in the storage of residual fuel oil, hydrogen sulfide and mercaptans are often encountered. The presence of hydrogen sulfide and mercaptans is objectionable because they often react with other hydrocarbons or fuel system components. Further, hydrogen sulfide and mercaptans are often highly corrosive as well as emit highly noxious odors. The toxicity of hydrogen sulfide in hydrocarbon streams is well known in the industry and uncontrolled emissions of hydrogen sulfide gives rise to severe health hazards. Burning of such vapors neither solves toxic gas problems nor is economical since light hydrocarbons have significant value. Considerable expense and efforts are expended annually to reduce the content of hydrogen sulfide in hydrocarbon streams to a safe level.
Nonregenerative scavengers for small plant hydrogen sulfide removal fall into four general categories: 1) aldehyde based, 2) metallic oxide based, 3) caustic based, and 4) other processes. In the removal of hydrogen sulfide by nonregenerative compounds, the scavenger reacts with the hydrogen sulfide to form a nontoxic compound or a compound, which can be removed from the hydrocarbon. For example, when formaldehyde reacts with hydrogen sulfide, a chemical compound known as form thionals (e.g., trithiane) is formed.
In large production facilities, it is generally more economical to install a regenerative system for treating sour gas streams. These systems typically employ a compound used in an absorption tower to contact the produced fluids and selectively absorb the hydrogen sulfide and possibly other toxic materials such as carbon dioxide and mercaptans. The absorption compound is then regenerated and reused in the system. Typical hydrogen sulfide absorption materials include alkanolamines, PEG, hindered amines, and other species that can be regenerated.
Treatments for removal of sulfhydryl compounds, such as hydrogen sulfide and mercaptans, from hydrocarbons and other substrates include the use of various reactive organic compounds. For example, U.S. Pat. No. 6,063,346 discloses the use of a combination of maleimides, formaldehydes, amines, carboxamides, alkylcarboxyl-azo compounds, and cumine-peroxide compounds for the removal of hydrogen sulfide and mercaptan contaminants from a fluid. Further, U.S. Pat. No. 5,128,049 discloses the use of certain morpholino and amino derivatives for the removal of hydrogen sulfide content from fluids. Low molecular weight aldehydes may also be combined with an alkyl or alkanolamine as disclosed in U.S. Pat. No. 4,748,011. Other aldehyde derived scavengers include the reaction product of low molecular weight alkanolamines and aldehydes as disclosed in U.S. Pat. No. 4,978,512.
PCT Application WO 92/01481 discloses a method of reducing sulfides in a sewage gas using certain tri-substituted-hexahydro-s-triazines. U.S. Pat. No. 5,347,004 discloses the use of 1,3,5 alkoxyalkylene hexahydro triazines. U.S. Pat. Nos. 5,128,049; 6,063,346; 8,512,449; and 8,734,637 disclose the use of triazines to remove hydrogen sulfide. U.S. Pat. No. 5,774,024 discloses the combination of an alkyl triazine scavenger and quaternary ammonium salt, where the quaternary ammonium salt enhances the effectiveness of the alkyl-triazine.
There is a continuing need for alternatives which may be useful in the removal and/or reduction of hydrogen sulfide from gaseous mixtures. Such alternatives include the development of new scavengers which are quick acting and which exhibit high affinity for removing hydrogen sulfide.